Stars

Problem Description
Many stars twinkling in the beautiful blue sky. The smart ACMer from earth, named Wiskey,sitting on a boat, thinking a stupid but hard problem: I want to use a balloon to contain all the stars in the sky, what's the smallest radius of the ballon?

Input
The input consists of multiple test cases. Each case begins with a line containing a positive integer n(2 <= n <= 10000), means the number of stars. Then following n lines each containing three positive integers (xi, yi, zi), indicates the coordinate of the i-th star in the sky.

Output
For each test case, output one line containing the smallest radius of a balloon used to contain all the stars in the sky. The answer should accurate up to 3 decimal places.

Sample Input
2
1 1 0
2 2 0

Sample Output
0.707